Hinge joint for dental articulator

ABSTRACT

A hinge joint for a dental articulator is provided with a hinge part in the form of a spherical element carried by the lower bow member and a hinge part carried by the upper bow member including anterior and posterior guide parts conjointly providing a condylar guide surface seated upon the spherical element and an abutment engaging the side of the spherical element. The posterior guide part may be selectively rocked about its own principal axis relative to the anterior guide part and/or selectively moved back and forth in an arcuate path orbitally about the spherical element relative to the anterior guide part.

United States Patent De Pietro [451 Jan. 25, 1972 [54] HINGE JOINT FORDENTAL ARTICULATOR Anthony J. De Pietro, 208 School Lane, Springfield,Pa. 19064 [22] Filed: Oct. 28, 1970 [21] Appl.No.: 84,585

[72] Inventor:

Primary ExaminerRobert Peshock Attorney-Louis V. Schiavo [5 7] ABSTRACTA hinge joint for a dental articulator is provided with a hinge part inthe form of a spherical element carried by the lower bow member and ahinge part carried by the upper bow member including anterior andposterior guide parts conjointly providing a condylar guide surfaceseated upon the spherical element and an abutment engaging the side ofthe spherical element. The posterior guide part may be selectivelyrocked about its own principal axis relative to the anterior guide partand/or selectively moved back and forth in an armate path orbitallyabout the spherical element relative to the anterior guide part.

12 Claims, 18 Drawing Figures PATENTED was 1972 SHEET 1 BF 4 I l lINVENTOR.

ANTHONY J. DEPIETRO BY J FIG. 5

0:44; 4 ra'w ATTORNEY.

PATENTED M25 5972 SHEET 2 OF 4 FIGQ8 INVENTOR. ANTHONY J. DEPIETRO 'q, zVIII. III/I'll Kym MP4 0 BY J (){OZLM ATTORNEY PATENIEU JANZS 19723.636. 634

sum 3 or 4 259 INVENTOR.

ANTHONY J. DEPIETRO d zw fi mzr ATTQRNEY.

' HINGE JOINT FOR DENTAL ARTICULATOR BACKGROUND OF THE INVENTION 1.Field of the Invention In my U.S. Pat. No. 3,478,431, issued Nov. 18,I969, I describe a certain hinge-type joint for a dental articulator.This application is addressed to further improvements in such joints. 1

2. Description of the Prior Art The hinge joint of my said patentincludes a hinge part in the form of a spherical element carried by thelower bow member and a hinge part carried by the upper bow member andprovided with a condylar guide surface seated upon the sphericalelement. The hinge part carried by the upper bow member is provided withanterior and posterior parts respectively providing anterior andposterior portions of the condylar guide surface. The posterior guidepart may be selectively positioned relative to the anterior guide partabout its own principal axis extending fore and aft of the joint.However, no provision is made for selectively moving the posterior guidepart back and forth in an arcuate path orbitally about the sphericalelement relative to the anterior guide part.

SUMMARY In a hinge joint constructed in accordance with the invention,the posterior guide part, in addition to being selectively positionablerelative to the anterior guide part about its principal axis extendingfore and aft of the joint, may be selectively shifted orbitally aboutthe spherical element relative to the anterior guide part. 1

Other objects of the invention will become apparent when the followingdescription is read with reference to the accompanying drawings, inwhich:

FIG. I is a side view of a hinge joint constructed in accordance withthe invention;

FIG. 2 is a rear view of the hinge joint, as indicated by lines IIII inFIG. 1;

FIG. 3 is afront view of the hinge joint, as indicated by lines III-IIIin FIG. 1;

FIG. 4 is a vertical longitudinal section on line IV-IV in FIG. 3;

FIG. 5 is a vertical transverse section on line V--\/ in FIG. 1;

FIG. 6 is a view, indicated by lines VIVI in FIG. I, showing only theprincipal parts of the hinge joint, the upper portion of the framemember or jacket being removed to expose the anterior and posteriorguide parts mounted therein;

FIGS. 7 and 8 are similar to FIG. 6, but show the posterior guide partin extreme positions;

FIG. 9 is an exploded perspective view of the hinge joint;

FIG. 10 is a side view of a modified form of the hinge joint;

FIG. I] is a rear view of the hinge joint, as indicated by lines XIXI inFIG. 10;

FIG. 12 is a front view of the hinge joint, as indicated by linesXII-XII in FIG. 1;

FIG. 13 is a vertical longitudinal section on line XIII--XIII in FIG.I2;

FIG. 14 is a vertical transverse section on line XIV-XIV in FIG. 1;

FIG. 15 is a view, indicated by lines XV-XV in FIG. 10, showing only theprincipal parts of the hinge joint, the upper portion of the framemember or jacket being removed to expose the anterior and posteriorguide parts mounted therein;

FIGS. 16 and 17 are similar to FIG. 15, but show the posterior guidepart in extreme positions; and

FIG. 18 is an exploded perspective view of the lower portion of theupper hinge part.

The following description is directed to the specific forms of theinvention shown in the drawings. It is not addressed to the scope of theinvention, which may be practiced in a wider variety of forms.

Referring to the drawings, and particularly to the embodiment shown inFIGS. 1-9, my improved hinge-type joint for the dental articulator isgenerally upright and may extend upwardly and rearwardly at an angle ofapproximately 10 relative to the vertical. It comprises an upper hingepart or assembly, generally designated 10, and a lower hinge part,generally designated I2. The assembly 10 includes a subassembly orcondyle guide means, generally designated 14, suspended from the upperbow member 16 by means of a second subassembly, generally designated 18.The lower hinge part I2 is provided with a neck 20 terminating in aspherical element 22, and the subassembly 14 is seated upon saidspherical element.

The subassembly 14 includes a frame member or jacket part 24 whichmounts posterior and anterior guide parts 26 and 28. The jacket 24generally is in the form of a hollow cylindrical main body part 30extending fore and aft of the joint and closed at the rear end thereofby a cross-axially extending part 32 of hollow semispherical shape. Thefore end and underside of the jacket are open. Extending in oppositedirections respectively from opposite sides of the jacket are a pair ofcoaxially related bosses 34.

The posterior guide part 26 is generally of solid semispherical shapeand is nested inthe hollow semispherical part 32 of the jacket, whichserves'as a socket for receiving the same. The part 26 is undercut toprovide a forwardly extending lip 36 overhanging the spherical element22. As shown in FIG. 4, the fore edge of the lip extends a shortdistance beyond the center of the spherical element 22, and as shown inFIG. 5, the lip does not extend all the way across the posterior guidepart, but terminates a short distance to the right of the verticallongitudinally extending median plane of the joint. The downwardlypresenting surface area 38 of the undercut merges smoothly with arounded surface area 30, which in turn merges smoothly with a forwardlypresenting surface area 42. As shown, the forwardly presenting face 44of the lip is beveled to assure freedom of movement of the posteriorguide part 26 in the socket part 32 of the jacket.

The rearwardly presenting semispherical surface of the posterior guidepart 26 is provided with a recess 46, and extending from the base of therecess rearwardly on the central axis of the part 26 is a stud 48. Thestud extends freely through a sleeve 50 which in turn extends through anarcuate slot 52 in the socket part 32 of the jacket. The fore end of thesleeve 50 is provided with a flange 54 accommodated by the recess 46.Threaded on the sleeve is a nut 56 which draws the flange tight againstthe socket part 32 of the jacket, and threaded on the stud is a nut 58which draws the posterior guide part 26 tight against the flange 54 ofthe sleeve 50. The portion 59 of the sleeve 50 between the flange 54 andthe nut 56 is rectangular in transverse section and coacts with theedges of the slot 52 to secure the sleeve 50 against turning about itslongitudinal axis.

The anterior guide part 28 is shaped as required for being nested in themain body part 30 of the jacket. In transverse section the upwardlypresenting surface area 60 thereof is arcuate in shape, and thedownwardly presenting surface area 62 thereof is straight and flat, asindicated in FIG. 3. In longitudinal section the surface area 60 isstraight and flat, and the surface area 62 is curvilinear, as shown inFIG. 4. The aft end portion of the part 28 is provided with surfaceareas 64 which converge or feather rearwardly respectively from oppositesides of the part 28 to form an upright edge 66 disposed in closeforwardly spaced relation to the fore edge of the lip 36. The lowerterminal of the edge 66 abuts the top of the spherical element 22. Thesurface areas 64 are disposed as required to accommodate movement of theposterior guide part 26 from the position thereof shown in FIG. 6 tothose is disposed just a short distance to the rear of the center of thespherical element 22, and the upwardly presenting surface area 72 of theabutment is disposed just a short distance above the center of thespherical element 22. The anterior guide part 28 may be turned relativeto the jacket about the central axis of the latter, and for selectivelypositioning the part 28 a bracket 76 is provided. The bracket is affixedto the fore end of the part 28 and extends upwardly and rearwardly overthe fore end of the jacket. A screw 78 serves to releasably fix the part28 in position.

The second subassembly 18 includes a member 80 with a base portion 82interconnecting a pair of laterally spaced arms 84 and 86 which embracethe jacket, as shown. A pair of coaxially related pivot screws 88 and 90extend freely respectively through the lower end portions of the armsand are threaded into the bosses 34 carried by the jacket. Extendingupwardly from the base 82 is a stem in the form of a tubular element 92projected freely through a slotted opening 94 in the upper bow member16. Threaded over the stem is a nut 96, and threaded into the stem is ascrew 98 the terminal portion of which is adapted to engage the back ofthe jacket, as shown.

It will be noted that the axis of the screw 98, designated Y- Y in FIG.I, the axis of the screws 88 and 90, designated XX in FIG. 3, and theprincipal axis of the posterior guide part 26, designated ZZ in FIG. I,intersect at the center of the spherical element 22, and that each ofthese axes is disposed at right angles to the others.

As shown and described, no component part of the upper hinge part ismovable relative to the upper bow member 16. In other words, the upperhinge part 10 is effectively locked in position. The spherical element22 is in starting position, i.e., one side thereof is engaged with theabutment 70 and the top thereof is nested close under the lip 36, asshown particularly in FIG. 4.

The nut 96 being threaded down on the stem 92 clamps the member 80 tothe upper bow member 16, and as a consequence, the upper hinge part 10is secured against movement laterally of the upper bow member andagainst turning about the upright axis YY. The screw 98 being threadeddown through the stem 92 bears down the back of the jacket andfrictionally secures the assembly 14 against pivotal movement about thehorizontal transverse axis XX. The nut 56 being threaded onto the sleeve50 clamps the latter to the jacket, and the nut 58 being threaded ontothe stud 48 clamps the posterior guide part 26 to the sleeve 50, as aconsequence of which the part 26 is secured against all movement in thesocket part 32 of the jacket. The screw 78 being threaded down throughthe bracket 76 engages the back of the jacket and secures the anteriorguide part 28 against movement in the main body part 30 of the jacket.

In adjusting the instrument and effectively locking it in adjustedposition, the first step is to move the lower hinge part 12 to thedesired position laterally of the instrument. Then the nut 96 isloosened and the upper hinge part 10 moved as a unit laterally of theinstrument to bring the abutment 70 into engagement with the inner sideof the spherical element 22. With the hinge part in such position andturned as required about the upright axis Y(, the nut 96 is retightened.

The screw 98 now may be turned out slightly to release the subassembly14 for tilting movement clockwise (as viewed in 'FIG. I) about thehorizontal-axis XX. With the subassembly I4 in the desired position, thescrew 98 is turned in again until the lower end thereof reengages theback of the jacket.

Now the nut 56 may be loosened slightly to release the sleeve 50 fromthe jacket, and then the posterior guide part 26 may be turned in thesocket part 32 of the jacket about the upright axis Y-Y by swinging thesleeve 50 and the stem 48 to the right or lefi as desired, within thelimits of the slot 52;

Thus the part 26 may be shifted back and forth orbitally in a circularpath about the spherical element 22. Extreme positions of the part 26are shown in FIGS. 7 and 8. With the sleeve 50 extending through thedesired portion of the slot 52, the nut 56 is retightened. Thereupon thenut 58 is loosened slightly to release the posterior guide part 26 fromthe flange 54 of the sleeve 50, whereupon the part 26 is turned aboutthe axis of the stud 48 to a desired position and the nut 58retightened.

The screw 78 now may be turned out slightly to release the anteriorguide part 28 from the jacket. Thereupon the part 28 is turned in thejacket about the axis ZZ to the desired position. With the part 28 inthe desired position, the screw 78 is retightened.

Suitable scales and index marks (not shown) may be provided to aid inmaking the aforementioned adjustments.

The upper and lower bow members may be opened and closed and shiftedrelative to one another fore and aft and laterally with the sphericalelement 22 always engaged with the condylar guide surface. As indicatedhereinabove, when the spherical element 22 is in starting position, oneside thereof is engaged with the abutment 70 and the top thereof isnested close under the lip 36. From this starting position, thespherical element 22 may move forth and back along any one of aplurality of diverging paths. It may move forth and back along theabutment 70 in contact therewith. It may move forth and back under thelip 36, being nested all the while in'the rounded surface area 40 of theundercut. While moving forth along the abutment 70, it may at the sametime move away from the same before returning to the starting position.

The anterior guide part 28 is only one of a set thereof, preferably madeof plastic material, each being provided with an undersurface having adifferent curvature. The selected part 28 is inserted and removed fromthe jacket through the open fore end thereof.

Now referring particularly to the embodiment of FIGS. 10-18, the jointfor the dental articulator is provided with a modified upper hinge partor assembly, generally designated 200. The assembly 200 includes asubassembly or condyle guide means, generally designated 202, suspendedfrom the upper bow member 16 by means of a second subassembly, generallydesignated 204. The subassembly 202 is seated upon the spherical elementor head 22 of the lower hinge part 12.

The subassembly 202 includes a frame member or jacket part 206 whichmounts posterior and anterior guide parts 208 and 210. The jacket 206generally is in the form of a round disc disposed upright and extendingfore and aft of the joint. The peripheral surface of the disc presentingupwardly and forwardly, designated 212, is arcuate in shape, and thedownwardly presenting surface of the disc, designated 214, is straightand flat and disposed below the center of the disc. The lower aftportion of the disc, designated 216, is rounded, the center of curvaturebeing at the center of the disc, midway between the opposite sidesthereof. The lower fore portion of the disc is hollowed out as requiredto accommodate the posterior and anterior guide parts 208 and 210, asshown.

The posterior guide part 208 is similar in every respect to theposterior guide part 26, and reference may be had to the description ofpart 26 hereinabove for all necessary details. A stud 218 extendsrearwardly from the part 208 on the central axis thereof and freelythrough a sleeve 220, which in turn extends through an arcuate slot 222in the lower aft portion or socket part 216 of the jacket. The fore endof the sleeve is provided with a flange 224 accommodated by a recess 226in the part 208. Threaded on the sleeve is a nut 228 which draws theflange tight against the socket part 216, and threaded on the stud is anut 230 which draws the posterior guide part 208 tight against theflange 224 of the sleeve 220. The portion 232 of the sleeve 220 betweenthe flange 224 and the nut 228 is rectangular in transverse section andcoacts with the edges of slot 222 to secure the sleeve 220 againstturning about its longitudinal axis.

In every essential respect, the anterior guide part 210 is similar tothe anterior guide part 28, and reference may be had to the descriptionof part 28 hereinabove for required details. It should be noted,however, that part 210 is generally rectangular in transverse section,being provided with a straight, flat upwardly presenting surface area234 and straight, flat opposite side surface areas 236. Thus part 210 isnot arranged for being selectively positioned relative to the jacket206. A screw 238 serves to releasably hold the part 210 in position. Inlongitudinal section the fore end of the part 210 is arcuately shaped tomerge smoothly with the arcuate surface 212 of the jacket. It will beunderstood that the anterior guide part 2l0, like the part 28, is onlyone of a set thereof, preferably made of plastic material, each beingprovided with an undersurface having a different curvature. The selectedpart 210 is inserted and removed from the jacket through the open foreend or bottom thereof.

The second subassembly 204 is provided with a yoke part 240 carried by ayoke mounting part 242 the stem of which extends through a sleeve 244.Threaded onto the sleeve is a lock nut 246, and threaded onto the stemof the yoke mounting part 242 is a lock nut 248. Threaded downwardlythrough the stem is a lock screw 250. The second subassembly 204 issimilar to the corresponding second subassembly 18 described in myaforementioned US. Pat. No. 3,478,43l, to which reference may be had fora detailed description. It should be noted that the two legs of the yoke240, designated 252 and 254, mount suitable coaxially related pivotelements 256 and 258 which extend freely respectively through said legsand are threaded into the opposite sides of the jacket. Threaded throughthe yoke leg 254 is a lock screw 259 the end of which engages the sideof the jacket to hold the jacket in adjusted position.

It will be noted that the axis of the screw 250, designated YY in FlG.10, the axis of the pivot elements 256 and 258, designated X-X in FIG.12, and the axis of the posterior guide part 208, designated Z-Z in FIG.10, intersect at the center of the spherical element 22, and that eachof the axes is disposed at right angles to the others.

The basic difference between the embodiment of FIGS. 1-9 and that ofFIGS. -18 is that in the latter embodiment the anterior guide part 210is fixed against movement relative to the jacket. Accordingly, in theoperation of the instrument, to

tilt the part 210 to either side, the lock screw 250 must be threadedout slightly to release the yoke 240, the subassembly 202 tilted as aunit to the desired position and then the lock screw 250 must beretightened. Reference may be had to my aforementioned US. Pat. No.3,478,431 for a description of the operation of the second subassembly204. In view of the detailed description of the operation of theembodiment of FIGS. l-9, any further description of the embodiment ofFIGS. 10-18 would appear to be unnecessary.

What is claimed is: 1. In a dental articulator, the combinationcomprising A. a lower bow member, B. an upper bow member, C. a pair oflaterally spaced hinge-type joints for mounting said lower bow membereach including i l. a hinge part in the form of a spherical elementcarried by said lower bow member, and 2. a hinge part carried by saidupper bow member includa. an anterior guide part,

b. a posterior guide part, said guide parts being provided with condylarguide surface areas conjointly extending over said spherical element andforwardly therefrom, means mounting said posterior guide part for beingturned selectively relative to said anterior guide part about aprincipal axis of said posterior guide part extending fore and aftand/or moved selectively relative to said anterior guide part orbitallyin a circular path about said spherical element,

d. means operable for adjustably fixing said posterior guide part in aselected position,

e. an abutment provided with an abutment surface engaging one side ofsaid spherical element and extending forwardly therefrom, and

f. means for mounting said anterior and posterior guide parts and saidabutment for movement as a unit about the center of said sphericalelement.

2. The combination according to claim 1 wherein the principal axis ofthe posterior guide part is generally horizontal and extends through thecenter of the spherical element, and the axis about which the posteriorguide part may be moved orbitally in a circular path is generallyupright and extends through the center of the spherical element.

3. The combination according to claim 2 wherein the condylar guidesurface area of the posterior guide part extends downwardly as well asrearwardly from the condylar guide surface area of the anterior guidepart and remains engaged with the spherical element throughout the fullrange of both turning and orbital movement of the posterior guide partwith respect to the anterior guide part.

4. The combination according to claim 3 wherein the abutment surface isdisposed in an upright position, and irrespective of the position of theposterior guide part within the range of its turning and/or orbitalmovement, the abutment surface and the rearwardly and downwardlyextending condylar guide surface area of the posterior guide part remainconstantly engaged with the spherical element when the anterior andposterior guide parts and the abutment are moved as a unit about saidspherical element.

5. The combination according to claim 4 wherein the assembly includes ahollow jacket having a main body part, and a socketed part with aforwardly presenting generally semispherical surface area, the posteriorguide part is provided with a corresponding rearwardly presentinggenerally semispherical surface area accommodated by the generallysemispherical surface area of said socketed part, said posterior guidepart being thereby nested in said socketed part for movement therein,the anterior guide part is mounted in said main body part of the jacket,and the abutment is carried by said anterior guide part in fixedrelation thereto.

6. The combination according to claim 5 wherein the posterior guide partis provided with a pivot element extending rearwardly therefrom throughan elongated opening in an arcuate wall area of said socketed jacketpart.

7. The combination according to claim 6 wherein the longitudinal axis ofthe pivot element and the center of the spherical element are disposedin the generally longitudinal median plane of the elongated opening.

8. The combination according to claim 7 wherein the posterior guide partis undercut to provide the condylar guide surface area thereof and alipoverhanging the spherical element and extending forwardly across anupright plane extending transversely through the center of the sphericalelement,

and the aft end portion of the anterior guide part feathers rearwardlyto a point disposed in an upright plane extending longitudinally throughthe center of the spherical element in forward spaced close relation tosaid lip whereby to provide clearance for orbital movement of saidposterior guide part.

9. The combination according to claim 8 wherein the point to which theanterior guide part feathers abuts the top of the spherical element.

10. The combination according to claim 7 wherein the means foradjustably fixing the posterior guide part against turning movement andagainst movement orbitally about the spherical elements are operable foreffecting said movements each independently of the other.

11. The combination according to claim 7 wherein a flanged sleeve isnonturnably projected through the elongated opening in the socketedjacket part, the flange of the sleeve is releasably clamped to thesocketed jacket part by a nut threaded on the sleeve, the pivot elementprojects freely through the sleeve, and the posterior guide part isreleasably clamped to said flange by a nut threaded on .said pivotelement.

12. The combination according to claim 7 wherein the anterior guide partis carried by the main body part of the jacket and is mounted thereinfor being selectively positioned relative thereto about the Centrallongitudinal axis of said main body part.

1. In a dental articulator, the combination comprising A. a lower bowmember, B. an upper bow member, C. a pair of laterally spaced hinge-typejoints for mounting said lower bow member each including
 1. a hinge partin the form of a spherical element carried by said lower bow member, and2. a hinge part carried by said upper bow member including a. ananterior guide part, b. a posterior guide part, said guide parts beingprovided with condylar guide surface areas conjointly extending oversaid spherical element and forwardly therefrom, c. means mounting saidposterior guide part for being turned selectively relative to saidanterior guide part about a principal axis of said posterior guide partextending fore and aft and/or moved selectively relative to saidanterior guide part orbitally in a circular path about said sphericalelement, d. means operable for adjustably fixing said posterior guidepart in a selected position, e. an abutment provided with an abutmentsurface engaging one side of said spherical element and extendingforwardly therefrom, and f. means for mounting said anterior andposterior guide parts and said abutment for movement as a unit about thecenter of said spherical element.
 2. a hinge part carried by said upperbow member including a. an anterior guide part, b. a posterior guidepart, said guide parts being provided with condylar guide surface areasconjointly extending over said spherical element and forwardlytherefrom, c. means mounting said posterior guide part for being turnedselectively relative to said anterior guide part about a principal axisof said posterior guide part extending fore and aft and/or movedselectively relative to said anterior guide part orbitally in a circularpath about said spherical element, d. means operable for adjustablyfixing said posterior guide part in a selected position, e. an abutmentprovided with an abutment surface engaging one side of said sphericalelement and extending forwardly therefrom, and f. means for mountingsaid anterior and posterior guide parts and said abutment for movementas a unit about the center of said spherical element.
 2. The combinationaccording to claim 1 wherein the principal axis of the posterior guidepart is generally horizontal and extends through the center of thespherical element, and the axis about which the posterior guide part maybe moved orbitally in a circular path is generally upright and extendsthrough the center of the spherical element.
 3. The combinationaccording to claim 2 wherein the condylar guide surface area of theposterior guide part extends downwardly as well as rearwardly from thecondylar guide surface area of the anterior guide part and remainsengaged with the spherical element throughout the full range of bothturning and orbital movement of the posterior guide part with respect tothe anterior guide part.
 4. The combination according to claim 3 whereinthe abutment surface is disposed in an upright position, andirrespective of the position of the posterior guide part within therange of its turning and/or orbital movement, the abutment surface andthe rearwardly and downwardly extending condylar guide surface area ofthe posterior guide part remain constantly engaged with the sphericalelement when the anterior and posterior guide parts and the abutment aremoved as a unit about said spherical element.
 5. The combinationaccording to claim 4 wherein the assembly includes a hollow jackethaving a main body part, and a socketed part with a forwardly presentinggenerally semispherical surface area, the posterior guide part isprovided with a corresponding rearwardly presenting generallysemispherical surface area accommodated by the generally semisphericalsurface area of said socketed part, said posterior guide part beingthereby nested in said socketed part for movement therein, the anteriorguide part is mounted in said main body part of the jacket, and theabutment is carried by said anterior guide part in fixed relationthereto.
 6. The combination according to claim 5 wherein the posteriorguide part is provided with a pivot element extending rearwardlytherefrom through an elongated opening in an arcuate wall area of saidsocketed jacket part.
 7. The combination according to claim 6 whereinthe longitudinal axis of the pivot element and the center of thespherical element are disposed in the generally longitudinal meDianplane of the elongated opening.
 8. The combination according to claim 7wherein the posterior guide part is undercut to provide the condylarguide surface area thereof and a lip overhanging the spherical elementand extending forwardly across an upright plane extending transverselythrough the center of the spherical element, and the aft end portion ofthe anterior guide part feathers rearwardly to a point disposed in anupright plane extending longitudinally through the center of thespherical element in forward spaced close relation to said lip wherebyto provide clearance for orbital movement of said posterior guide part.9. The combination according to claim 8 wherein the point to which theanterior guide part feathers abuts the top of the spherical element. 10.The combination according to claim 7 wherein the means for adjustablyfixing the posterior guide part against turning movement and againstmovement orbitally about the spherical elements are operable foreffecting said movements each independently of the other.
 11. Thecombination according to claim 7 wherein a flanged sleeve is nonturnablyprojected through the elongated opening in the socketed jacket part, theflange of the sleeve is releasably clamped to the socketed jacket partby a nut threaded on the sleeve, the pivot element projects freelythrough the sleeve, and the posterior guide part is releasably clampedto said flange by a nut threaded on said pivot element.
 12. Thecombination according to claim 7 wherein the anterior guide part iscarried by the main body part of the jacket and is mounted therein forbeing selectively positioned relative thereto about the centrallongitudinal axis of said main body part.